Re: [LARTC] Load Balance and SNAT problem.

[Peter Rabbitson <rabbit@rabbit.us>]

Grant Taylor wrote:
> On 6/27/2007 3:03 AM, Peter Rabbitson wrote:
>> I want the kernel to be able to realize that a gateway is no good for
>> any destinations other than the specified netblock.
> 
> Would it be fair to say that you are wanting an administratively 
> configurable "ignore addresses that fall with in this <network>" while 
> deciding if a gateway is dead?
> 
> Obviously <network> would need to be a bit more than just an ip / 
> netmask combination to make this realistic.
> 
> If this is what you are wanting, it may be possible to augment the 
> kernel code that is used to detect dead gateways and have it check to 
> see if the networks match a list (from somewhere in proc / sysfs / 
> sysctl?) and not increment traffic counters.  I am presuming that it is 
> the traffic counters that have to be incremented for the kernel to think 
> that a route is still alive.  So, if you purposfully did not increment 
> the counters, you could probably detect that a given gateway is no good. 

Something along these lines, yes. Except that instead of a 
packet-counter there is a resettable timer, that gets reset anytime a 
matching packet comes in. When the timer goes over a specified limit - 
gateway is dead.

>  I think you would have to add an additional route that was to the given 
> network(s) that did not use such a feature to provide a way for the 
> routing code to route to those network(s) that it no longer would get to 
> via a default gateway.
> 

This would be a manual task for the administrator, there is no place for 
this in-kernel.

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